1. Field of the Invention
The invention relates to a process for producing 7.beta.-amino-7.alpha.-methoxycephalosporins and, more particularly, it relates to a process for producing 7.beta.-amino-7.alpha.-methoxycephalosporanic acid compounds from 7.beta.-acylamino-7.alpha.-methoxycephalosporanic acid compounds without the accompanying epimerization at the 7-position thereof.
2. Description of the Prior Art
Hitherto, as a process for releasing the acyl group of 7-acylamino-7-methoxycephalosporanic acid compound, there is known a process wherein the cephalosporanic acid compound is reacted with a halogenating agent such as phosphorus pentachloride, etc., to form the corresponding iminohalide and then the iminohalide is reacted with a lower alcohol under anhydrous conditions (see, U.S. Pat. No. 3,956,286). However, in the known process, the reaction is performed at temperatures of from 0.degree. C. to room temperature and the inventor himself clarified that the reaction is accompanied by epimerization to form more than twice the amount of the 7.beta.-methoxy epimer than the 7.alpha.-methoxy epimer (see, "Tetrahedron Letters"; No. 14, 1307-1310 (1974)).
In a series of 7-amino-7-methoxycephalosporanic acid compounds, the compounds having antimicrobial activity useful as medicaments are restricted to the 7.alpha.-methoxy compounds in which the methoxy group at the 7-position possesses an .alpha.-steric configuration but since according to the above-described conventional process, the product is obtained as a mixture of the 7.alpha.-methoxy epimer and the 7.beta.-methoxy epimer, it is required to isolate the objective compound from the mixture. It has been pointed out as a difficulty in the conventional process that these epimers are not easily separated from each other.